he various ethno-cultural groups of the Ottoman Empire could not always be neatly classified into a single millet as some subgroups embraced many religions and dogmas. The Arvanites are an interesting case, not only because of internal religious diversity, but also because they moved around and settled in different areas. Some Arvanites tribes in southern Albania became Christian Orthodox; others in the north converted to Catholicism, while a further group embraced Islam. The infertile soil of their country, the wars against the Ottomans which endured until the end of the 14th century, together with the political and economic conditions in the Balkans, prompted certain groups to migrate south to the islands of the Aegean. This movement began in the 15th century, intensified in the latter part of the 16th and reached its peak in the 17th century. Having settled, the Arvanites tended to work on the land and occupy themselves with cattle-breeding. Some offered their services as mercenaries in the pay of local rulers. However, between the 18th and 19th centuries nationalist ideologies began to gather force within the Empire and a sizeable proportion of the population developed a Greek consciousness, and went on to participate in the Greek Revolution of 1821.